This is a skewed test to make RNG damage look bad, if anything you should compare it to Jishnu's Radiance (which on a good rng deals similar if not way more than Hi on spikes.) You can't compare apples to oranges and expect the oranges to be considered the inferior fruit on the taste test.

Hi has larger FTP, an offhand hit+chance to triple/double attack proc, and higher WSC mods. Heavy Shot is just a plain awful comparison.